A variety of assays can be performed using an assay chip that includes one or more sensors positioned on a substrate. A cartridge can be employed to transport various liquids to the sensors. The cartridge typically includes one or more reservoirs that each holds one of the solutions. During the operation of the cartridge, the cartridge is inserted into a machine that causes the liquids in the reservoirs to be transported to the one or more sensors. The machine can then operate the one or more sensors so as to perform the assay.